Quantum dots are particles made from nanomaterials that emit light of specific frequencies upon the application of an electrical current or light. The frequencies of the light emitted by the quantum dots may be varied by changing the dots' size, shape, and type of material. One application of quantum dots are electro-optic displays, specifically, LED displays, because of the potential for improved color accuracy.
The term “electro-optic”, as applied to a material or a display, is used herein in its conventional meaning in the imaging art to refer to a material having first and second display states differing in at least one optical property, the material being changed from its first to its second display state by application of an electric field to the material. Although the optical property is typically color perceptible to the human eye, it may be another optical property, such as optical transmission, reflectance, luminescence, or in the case of displays intended for machine reading, pseudo-color in the sense of a change in reflectance of electromagnetic wavelengths outside the visible range.
Quantum dots are commonly incorporated into an LED display by being provided in the form of a film that is laminated between a back-light unit and a red-green-blue (RGB) color filter. The back-light unit comprises a blue LED and a portion of the emitted blue light is converted into red and green light after passing through the quantum dot film. Therefore, the light exiting the quantum dot film and entering the color filter includes a substantially increased portion of red, green, or blue light. As a result, the amount of light that is absorbed by the color filter is reduced.
Quantum dot films are manufactured by blending quantum dots in a polymer, such as an epoxy, and applying a barrier layer on either side of the layer of polymer-quantum dot blend. The cured polymer and barrier layers seal the quantum dots from oxygen and water, which may degrade the material over time. However, there are frequently difficulties inherent in mixing quantum dots and polymers, such as homogeneity, dispersibility, and performance loss (quantum yield and reliability). Thus, there is a need for improved quantum dot films.